Main line water pressure

I have installed a set of sprinkler heads (3 1/4 spray heads ans 2 1/2 spray heads)that use 6GPM using one zone. Distance from one sprinkler head to another is max 20ft. I am using the water supply from the lawn water faucet. The water pressure seems a little low. The pressure from the open water faucet is 50psi. I don't detect any leaks.Should I have about the same pressure if I tap into water faucet or the main water line? I should have about 15gpm available with 50psi. thanks

If I understand your question correctly you tied in to a hose bib off of the house close to the lawn. That would also indicate that you may have some small pipe in the house that the water is flowing through to get to your sprinkler heads. It is also loosing pressure through every turn and piece of pipe. The idea of tieing in to the largest, best source close to the water meter or pump is the way to go. You may also get less water hammer or future plumbing problems by stressing you indoor house plumbing as you may be doing at this time.

For pulling 6gpm, you need to tie into the mainline before it enters the house.

The reason I say that is because your hose bibb is most likely fed by a 1/2" copper water line (or modern equivilent). Loss charts indicate that 6gpm through a 1/2" water line puts the water velocity in the danger zone (faster than 5 ft/s). For a 6gpm flow, you need a minimum of 3/4" copper or 3/4" PVC AT A MINIMUM. Your water line between the meter and the house is likely to be 1" PVC (or something similar). So if you tie into that with a 3/4" or 1" line feeding your irrigation system, you'll get those water velocities down.

Now as for your pressure problem... well trying to ram 6gpm through 1/2" pipe is going to loose some pressure. Assuming 1/2" copper, you will be loosing about 30psi for every 100' of pipe. So just switching from 1/2" source to a 3/4" or 1" source is going to get you back some pressure. How ever, it's sort of funny that your pressure just happens to be about 50psi. That is the default setting for most pressure regulators. So it sounds like it is possible that you have a pressure regulator in your home and you are pulling water from a hose bibb that is AFTER the pressure regulator and not the one before it. Most homes have two hose bibbs, and usually one is before any regulators and one is usually after it. So try checking the pressure of the other hose bibb and see if it isn't greater than 50psi.

So it might be possible that you will gain pressure in three ways by tying into the water main between the meter and the house:
1. Larger Pipe - less friction losses
2. Less Pipe - less friction losses
3. Unregulated - starting pressure might be greater than 50psi.

Tap intop the maiinline

Good answers !

Two other thoughts. If you use your water spigot, you may hear the water runing whenever the irrigation system is on. Possibly a problem if you are irrigating in the early A.M., and anyuone wishes to sleep in.

Another consideration, is the design of your system. Your present system may work, but if you put all heads on one line,the last will not spray as much do th the pressure lossin the pipe. As an alternative, if you "T" right off the line at the spigot, and run two lines, the pressure loss to the distal heads wil be less. On some systems, attaching the two legs to form a loop, often solves the problem. Also, consider running a larger line in ground, 3/4 inch schedule 40 at minimum.

My recommendation, tap into the mainline, installa proper bacf flow device, and run a 1 inch mainline to which you can tap for several zones. I mostly use 1" sch 40 everywhere, as I have to stock fewer sizes of fitting.

main line water source

I checked the main water line and it seems to use a 1/2 copper pipe. With 50psi that still gives me about 6.5gpm if my calculations are correct. The reason I was just using the faucet is I didn't know if it was legal for me to tap into the main water line without a professional doing it. I did check on it and for a plumber doing it, it would cost about $700 to connect to the main water line and with a double check valve. That is a little steep for me at this time. My system I just started (just the right front side of my yard) seems to do OK using 6gpm but anything above that would be pushing it. I could make it work but I would have to use alot of zones, 6.5gpm per zone. Don't most residental systems have a minimum of 12gpm?

I checked the front and back and both faucets bibs reads 50psi. Right now I am using a 3/4" pvc coming off the faucet header line and then using 1/2" pvc lateral line to sprinkler head. My main line close to the meter is using a 1/2" copper pipe with 50psi that is 6.5 gpm.

You said 6gpm going through a 1/2" copper pipe reaches the danger zone. Does this mean I could have a pipe inside my house burst by setting up this type of system using the ouside faucet? If that is the case it would be better if I did use the main water line. thanks for your help

I will probably get some heat for this, but. First of all, it is really hard to believe that your mainline is 1/2 copper. It is possible of course. It would be my first to see, and I learn new things everyday. You could maybe get around the double check issue if you use AVB valves by rainbird. You may have to check too see if your city will allow. Are you getting a permit for this job or not.

Also 700.00 seems a little High for a tie in and a 1/2, 3/4 Double Check assembly. Also The Doublecheck assembly will steal more pressure than an AVB on the rainbird valves or a PVB. Is elevation an issue? I know this all sounds like a big pain in the keester, but we are all trying to help you as best we can to get this done as efficiently as possible.
You may see if you have an irrigator that can do the tie in cheaper than a plumber. I will bet they will.

I gave you a lot to sift through and I am sure this will get some comments from the other pros out there as well.
Good Luck.

I checked the front and back and both faucets bibs reads 50psi. Right now I am using a 3/4" pvc coming off the faucet header line and then using 1/2" pvc lateral line to sprinkler head. My main line close to the meter is using a 1/2" copper pipe with 50psi that is 6.5 gpm.

You said 6gpm going through a 1/2" copper pipe reaches the danger zone. Does this mean I could have a pipe inside my house burst by setting up this type of system using the ouside faucet? If that is the case it would be better if I did use the main water line. thanks for your help

By "danger zone", you run the risk of water hammer which can cause damage inside the house. I doubt a properly soildered 1/2" copper pipe is going to burst, but some weak point, perhaps a connector or the hose that feeds things like the dish washer, the toilets, or washing machines could break. Basically, most indoor plumbing is only speced for 50psi. When you get water hammer (loud bang caused when high velocity water suddenly stops moving because a valve quickly closed), that causes a water pressure spike in the plumbing. That pressure spike is what, over time, could lead to the failure of some part of the plumbing system. So if you're mainline from the meter to the house really is 1/2" (usually from what I've seen and heard, that's usually 3/4" copper or 1" PVC or similar), then you want to tie into that pipe as early as possible to minimize the possibility of water hammer and to minimize pressure losses. When it comes to water hammer, where you tie into the mainline doesn't matter. If you have water hammer, the pressure spike will go through the entire house. But by tying in as close to the meter as possible and immediately upsizing to 1"PVC, you'll minimize the possibility of water hammer.

If you read over the online guide www.irrigationtutorials.com, you will see that the expert that put this totorial together basically says that 1/2" pipes have no place in irrigation. Basically, the pressure losses are just too great. So I would agree with hi.todd and suggest that you use 3/4" Sch40 PVC at a minimum, and because it allows for even less pressure losses without much of a price increase, that you instead use 1" PCV. Basically, so much 1" and 3/4" PVC is used, that the prices between the two are relatively small for the common components. You don't see a major price jump until you start getting into the 1-1/4" and above sizes. When it comes to irrigation, for many reasons, bigger is always better (in terms of sizing pipes). So if you haven't purchased the materials, I'd suggest 1" Sch40 PVC for your main line AND latterals. For one thing, it will make purchasing parts and spare parts easier since everything will be 1". For the irrigation system I put in my yard, the only place I used anything smaller than 1" was the 3/4" pipes I used for drip irrigation latterals. Otherwise, I used 1" right to each sprinkler head.

I always heard to go up one size from your main line that is why I used a 3/4"pvc pipe. So, if I was coming off of a 1/2' pipe it would still be ok to go up to a 1" pvc pipe and then use 3/4" pvc pipe for lateral line to sprinkler heads. thanks for your help